Prehistoric rhino reveals secrets

The preserved body of a woolly rhinoceros has revealed new insights into how this now extinct giant animal once lived.

Melting corpse of the Kolyma woolly rhino [Credit: Quaternary Science Reviews/http://dx.doi.org/10.1016/j.quascirev.2011.02.010,]

The woolly rhino was once one of the most abundant large mammals living in Eurasia, but only a handful of preserved carcasses have been found.

Now an analysis of a female woolly rhino found preserved in Siberia reveals that the animal was a herbivore that grazed mainly on cereals, and was similar in size to today's Javan rhino.

However, it was slow to reproduce, had a short stubby tail and ears, and was likely driven to extinction in part due to its inability to wade through deeper blankets of snow, which became more common as the climate changed, say scientists.

Details of the discovery are published in the journal Biology Bulletin.

Woolly rhino (Coelodonta antiquitatis) remains have been found spanning Eurasia, from the UK in the west to Chukotka and Kamchatka in the Russian far east.

But few whole skeletons have been discovered and only four whole carcasses, including the animal's soft tissues as well as the bones, have survived.

Left half of the Kolyma woolly rhino mummy [Credit: Quaternary Science Reviews/http://dx.doi.org/10.1016/j.quascirev.2011.02.010]

These remains allowed scientists to determine that the woolly rhino had a long body and short legs, a flattened front horn and thick skin covered by a coat of thick fur.

Those insights have now been added to, following a study by Gennady Boeskorov from the Russian Academy of Sciences in Yakutsk.

He analysed a woolly rhino carcass first discovered in 2007, in the lower reaches of the Kolyma River. The animal was found buried at a depth of five to nine metres from the surface of the opening of a gold mine.

The female rhino lived 39,000 years ago.

Her head, with two horns, remains together with much of her trunk and all four legs. Most internal organs have been lost, but her stomach and its contents are intact.

Separate remains of the Kolyma rhino: a – skull, b – anterior horn, c – posterior horn, d – humerus, e – ulna, f – pelvis, g – lower part of hind right leg [Credit: Quaternary Science Reviews/http://dx.doi.org/10.1016/j.quascirev.2011.02.010]

Dr Boeskorov studied the woolly rhino's features, comparing it to those of modern rhinos.

His study confirms that the woolly rhino had thick brown skin and fur, and was a heavy lumbering animal, weighing around 1.5 tons, with dimensions similar to that of a modern Javan rhino.

Its feet would have placed a pressure on the ground of 1.8kg per square centimetre, more than three times that of a modern moose.

The female rhino had an udder with two nipples, making it likely that woolly rhinos gave birth to one, or occasionally two calves.

It also had a short, fur-covered tail compared to modern rhinos and short, lancet-shaped ears - much narrower than those of its living relatives. The ears match the shape of those drawn in artwork by Palaeolithic humans on cave walls. These shortened extremities are likely to have been adaptations to a cold climate.

But the snow in which the woolly rhino lived ultimately proved its undoing.

Cave art depicting a woolly rhino in the Chauvet cave, France [Credit: Inocybe]

The rhino's thick skin and long fur made it initially well adapted to the cold, dry climate of the late Pleistocene.

However, its considerable body weight, short legs and the huge pressures imposed by its feet would have made tackling deep snow difficult.

Modern ungulates such as the saiga and musk ox find it difficult to move in snow layers thicker than 30cm.

If the snow reaches their bellies, these animals become almost helpless.

As the late Pleistocene gave way to the early Holocene, climate warming and moistening created deeper layers of snow in winter, and a similar fate is likely to have befallen the woolly rhino, said Dr Boeskorov.

Reconstruction of a woolly rhino [Credit: Michael Long/NHMPL]

"It is quite likely [this] factor played an important role in the extinction of the woolly rhinoceros," writes Dr Boeskorov in the journal.

As this ice and snow melted, the landscape of the time would also have become increasingly pitted with hollows and boggy banks, forming natural traps that woolly rhinos might have found impassable.

"In addition, the natural traps presented certain danger for such a short-legged and heavy creature."

"Presumably, this rhinoceros slumped, bogged down and drowned in such a trap."

Author: Matt Walker | Source: BBC News Website [December 06, 2012]